Fix for Memory Leak (#660)

* Fix for Memory Leak

#659

* Update MemoryLeakTests.cs

* Remove ReadOnlyCollectionPooled

Use ReadOnlyDisposableCollection

Author: ChrisPulman

samples/Directory.build.props

@@ -2,7 +2,6 @@
   <PropertyGroup>
     <Nullable>enable</Nullable>
     <AvaloniaVersion>11.0.10</AvaloniaVersion>
-    <CodeAnalysisRuleSet>$(MSBuildThisFileDirectory)..\src\analyzers.ruleset</CodeAnalysisRuleSet>
     <WarningsAsErrors>CS8600;CS8602;CS8603;CS8604;CS8605;CS8606;CS8607;CS8608;CS8609;CS8610;CS8611;CS8612;CS8613;CS8614;CS8615;CS8616;CS8617;CS8618;CS8619;CS8620;CS8621;CS8622;CS8623;CS8624;CS8625</WarningsAsErrors>
   </PropertyGroup>
   <ItemGroup>

src/Directory.build.props

@@ -27,6 +27,7 @@
     <LangVersion>preview</LangVersion>
     <EnableNETAnalyzers>True</EnableNETAnalyzers>
     <AnalysisLevel>latest</AnalysisLevel>
+		<NoWarn>$(NoWarn);IDE1006</NoWarn>
   </PropertyGroup>
 
   <ItemGroup>
@@ -35,17 +36,16 @@
     <None Include="$(MSBuildThisFileDirectory)..\README.md" Pack="true" PackagePath="\" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(IsTestProject)' != 'true'">
-    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All" /> 
-  </ItemGroup>
-  <ItemGroup>
-    <PackageReference Include="Nerdbank.GitVersioning" Version="3.6.133" PrivateAssets="all" />
-    <PackageReference Include="stylecop.analyzers" Version="1.2.0-beta.556" PrivateAssets="all" />
-    <PackageReference Include="Roslynator.Analyzers" Version="4.12.2" PrivateAssets="All" />
-  </ItemGroup>
-  <ItemGroup>
-    <AdditionalFiles Include="$(MSBuildThisFileDirectory)stylecop.json" Link="stylecop.json" />
-  </ItemGroup>
+	<ItemGroup Condition="'$(IsTestProject)' != 'true'">
+		<PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All" />
+	</ItemGroup>
+	<ItemGroup>
+		<PackageReference Include="Nerdbank.GitVersioning" Version="3.6.133" PrivateAssets="all" />
+		<PackageReference Include="stylecop.analyzers" Version="1.2.0-beta.556" PrivateAssets="all" />
+		<PackageReference Include="Roslynator.Analyzers" Version="4.12.2" PrivateAssets="All" />
+	</ItemGroup>
+	<ItemGroup>
+		<AdditionalFiles Include="$(MSBuildThisFileDirectory)stylecop.json" Link="stylecop.json" />
+	</ItemGroup>
 
- </Project>
- 
+</Project>

src/ReactiveUI.Validation.Tests/MemoryLeakTests.cs

@@ -37,28 +37,20 @@ public void Instance_Released_IsGarbageCollected()
         new Action(
             () =>
             {
-                var sut = new TestClassMemory();
+                var memTest = new TestClassMemory();
 
-                reference = new WeakReference(sut, true);
-                sut.Dispose();
+                reference = new WeakReference(memTest, true);
+                memTest.Dispose();
             })();
 
-        // Sut should have gone out of scope about now, so the garbage collector can clean it up
+        // memTest should have gone out of scope about now, so the garbage collector can clean it up
         dotMemory.Check(
             memory => memory.GetObjects(
                 where => where.Type.Is<TestClassMemory>()).ObjectsCount.Should().Be(0, "it is out of scope"));
 
         GC.Collect();
         GC.WaitForPendingFinalizers();
 
-        if (reference.Target is TestClassMemory sut)
-        {
-            // ReactiveObject does not inherit from IDisposable, so we need to check ValidationContext
-            sut.ValidationContext.Should().BeNull("it is garbage collected");
-        }
-        else
-        {
-            reference.Target.Should().BeNull("it is garbage collected");
-        }
+        reference.IsAlive.Should().BeFalse("it is garbage collected");
     }
 }

src/ReactiveUI.Validation.Tests/Models/TestClassMemory.cs

@@ -31,7 +31,7 @@ public TestClassMemory()
             .DisposeWith(_disposable);
 
         // commenting out the following statement makes the test green
-        ValidationContext.ValidationStatusChange
+        ValidationContext?.ValidationStatusChange
             .Subscribe(/* you do something here, but this does not matter for now. */)
             .DisposeWith(_disposable);
     }

src/ReactiveUI.Validation.Tests/ValidationContextTests.cs

@@ -125,14 +125,15 @@ public void IsValidShouldNotifyOfValidityChange()
         viewModel.ValidationContext.Add(nameValidation);
 
         var latestValidity = false;
-        viewModel.IsValid().Subscribe(isValid => latestValidity = isValid);
+        var d = viewModel.IsValid().Subscribe(isValid => latestValidity = isValid);
         Assert.False(latestValidity);
 
         viewModel.Name = "Jonathan";
         Assert.True(latestValidity);
 
         viewModel.Name = string.Empty;
         Assert.False(latestValidity);
+        d.Dispose();
     }
 
     /// <summary>
@@ -220,4 +221,4 @@ public void ShouldClearAttachedValidationRulesForTheGivenProperty()
         Assert.NotEmpty(viewModel.ValidationContext.Text);
         Assert.Equal(name2ErrorMessage, viewModel.ValidationContext.Text.ToSingleLine());
     }
-}
+}

src/ReactiveUI.Validation/Collections/ReadOnlyCollectionPooled.cs

@@ -0,0 +1,60 @@
+// Copyright (c) 2024 .NET Foundation and Contributors. All rights reserved.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+
+namespace ReactiveUI.Validation.Collections;
+
+internal sealed class ReadOnlyDisposableCollection<T>(IEnumerable<T> items) : IReadOnlyCollection<T>, IDisposable
+{
+    private readonly ImmutableList<T> _immutableList = ImmutableList.CreateRange(items);
+    private bool _disposedValue;
+
+    /// <summary>
+    /// Gets the number of elements in the collection.
+    /// </summary>
+    public int Count => _immutableList.Count;
+
+    /// <summary>
+    /// Returns an enumerator that iterates through the collection.
+    /// </summary>
+    /// <returns>
+    /// An enumerator that can be used to iterate through the collection.
+    /// </returns>
+    public IEnumerator<T> GetEnumerator() => _immutableList.GetEnumerator();
+
+    /// <summary>
+    /// Returns an enumerator that iterates through a collection.
+    /// </summary>
+    /// <returns>
+    /// An <see cref="T:System.Collections.IEnumerator"></see> object that can be used to iterate through the collection.
+    /// </returns>
+    IEnumerator IEnumerable.GetEnumerator() => _immutableList.GetEnumerator();
+
+    /// <summary>
+    /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
+    /// </summary>
+    public void Dispose()
+    {
+        Dispose(disposing: true);
+        GC.SuppressFinalize(this);
+    }
+
+    private void Dispose(bool disposing)
+    {
+        if (!_disposedValue)
+        {
+            if (disposing)
+            {
+                _immutableList.Clear();
+            }
+
+            _disposedValue = true;
+        }
+    }
+}

src/ReactiveUI.Validation/Collections/ReadOnlyDisposableCollection{T}.cs

@@ -6,7 +6,6 @@
 using System;
 using System.Buffers;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Reactive.Concurrency;
 using System.Reactive.Disposables;
@@ -31,15 +30,16 @@ namespace ReactiveUI.Validation.Contexts;
 /// </remarks>
 public class ValidationContext : ReactiveObject, IValidationContext
 {
+    private readonly CompositeDisposable _disposables = [];
+
     private readonly ReplaySubject<IValidationState> _validationStatusChange = new(1);
     private readonly ReplaySubject<bool> _validSubject = new(1);
 
-    private readonly IConnectableObservable<bool> _validationConnectable;
+    private readonly IObservable<bool> _validationObservable;
     private readonly ObservableAsPropertyHelper<IValidationText> _validationText;
     private readonly ObservableAsPropertyHelper<bool> _isValid;
 
-    private readonly CompositeDisposable _disposables = [];
-    private SourceList<IValidationComponent> _validationSource = new();
+    private readonly SourceList<IValidationComponent> _validationSource = new();
     private bool _isActive;
 
     /// <summary>
@@ -52,15 +52,14 @@ public ValidationContext(IScheduler? scheduler = null)
         var changeSets = _validationSource.Connect().ObserveOn(scheduler);
         Validations = changeSets.AsObservableList();
 
-        _validationConnectable = changeSets
+        _validationObservable = changeSets
             .StartWithEmpty()
             .AutoRefreshOnObservable(x => x.ValidationStatusChange)
             .QueryWhenChanged(static x =>
                 {
-                    using ReadOnlyCollectionPooled<IValidationComponent> validationComponents = new(x);
+                    using ReadOnlyDisposableCollection<IValidationComponent> validationComponents = new(x);
                     return validationComponents.Count is 0 || validationComponents.All(v => v.IsValid);
-                })
-            .Multicast(_validSubject);
+                });
 
         _isValid = _validSubject
             .StartWith(true)
@@ -95,7 +94,7 @@ public IObservable<bool> Valid
     /// <summary>
     /// Gets get the list of validations.
     /// </summary>
-    public IObservableList<IValidationComponent> Validations { get; private set; }
+    public IObservableList<IValidationComponent> Validations { get; }
 
     /// <inheritdoc/>
     public bool IsValid
@@ -162,10 +161,7 @@ public IValidationText Text
     /// <inheritdoc/>
     public void Dispose()
     {
-        // Dispose of unmanaged resources.
         Dispose(true);
-
-        // Suppress finalization.
         GC.SuppressFinalize(this);
     }
 
@@ -183,11 +179,8 @@ protected virtual void Dispose(bool disposing)
             _validationStatusChange.Dispose();
             _validSubject.Dispose();
             _validationSource.Clear();
-            Validations.Dispose();
             _validationSource.Dispose();
-
-            Validations = null!;
-            _validationSource = null!;
+            Validations.Dispose();
         }
     }
 
@@ -199,7 +192,7 @@ private void Activate()
         }
 
         _isActive = true;
-        _disposables.Add(_validationConnectable.Connect());
+        _disposables.Add(_validationObservable.Subscribe(_validSubject));
     }
 
     /// <summary>